Question

Consider a current carrying wire (current I) in the shape of a circle. Note that as the current progresses along the wire, the direction of j (current density) changes in an exact manner, while the current I remain unaffected. The agent that is essentially responsible for is ______.

विकल्प

• source of emf.

• electric field produced by charges accumulated on the surface of wire.

• the charges just behind a given segment of wire which push them just the right way by repulsion.

• the charges ahead.

Answer 1

Consider a current carrying wire (current I) in the shape of a circle. Note that as the current progresses along the wire, the direction of j (current density) changes in an exact manner, while the current I remain unaffected. The agent that is essentially responsible for is electric field produced by charges accumulated on the surface of wire.

Explanation:

Current per unit area (taken normal to the current), I/A, is called current density and is denoted by `vecJ`.

The SI unit of the current density ate A/m². The current density is also directed along E and which is also a vector quantity and the relationship is given by

`vecJ = σvecE = vecE/ρ`

Where σ = conductivity and ρ = resistivity or specific resistance of the substance.

The `vecJ` changes due to the electric field produced by changes accumulated on the surface of wire.